Vitamin D deficiency is relatively common, and its management in patients with sarcoidosis is challenging due to the risk of hypercalcaemia. Our patient had an autologous stem cell transplant for multiple sclerosis and was given high-dose vitamin D concurrently with immunosuppressive therapy. The patient subsequently presented with symptomatic hypercalcaemia and an acute kidney injury. A clinical and biochemical recovery was reached by withdrawing vitamin D and administering intravenous fluids. Interestingly, new evidence suggests that activated vitamin D can actually dampen the inflammatory process in sarcoidosis, and this was reflected in a reduction of our patient's serological markers of sarcoidosis activity. One large study found no significant risk of hypercalcaemia when low doses of vitamin D were used in sarcoidosis. Where indicated, and until clear guidelines are established, we suggest using low doses of vitamin D with cautious monitoring of calcium and renal function.